The subject invention relates to a programmable controller for controlling the operation of mechanical systems. More particularly it relates to a microprocessor based controller particularly suited for control of paper handling systems.
Controllers for mechanical systems are well known. Such systems provide control signals to a mechanical system to control the operation of actuators such as motors and solenoids in response to commands from a host computer system and signals from sensors in the mechanical system. For mechanical systems such as paper handling systems which transport and perform operations on a work piece such as a sheet of paper, an envelope, or a completed mail piece, such controllers are sometimes referred to as motion controllers. In recent years, with the steadily increasing availability and decreasing cost of microprocessors, such controllers have most often been implemented as programmable controllers based upon a dedicated microprocessor.
While generally such programmable controllers have functioned well they have typically suffered from certain problems and disadvantages. Even with the high speed of modern microprocessors in complicated mechanical systems where numerous functions must be controlled simultaneously the processing load on such controllers is often so great that the load must be divided among a number of dedicated microprocessors. Where such controllers are programmed independently to control differing functions the typical result is that each microprocessor will operate in a way which bears little relation to other microprocessors in the system, increasing the system complexity and decreasing system maintainability. Further, once such controllers have been programmed the program structure and the rates at which sensors in the mechanical system are sampled and control signals are generated for the mechanical system are substantially fixed; requiring that the initial program anticipate the full range of possible operating conditions or accept less than optimal performance for other than nominal conditions.
Additionally, it would be highly desirable to provide a programmable controller, and particularly a programmable motion controller, which would be suitable for a wide range of applications.
Thus it is an object of the subject invention to provide a programmable controller, and particularly a programmable motion controller, which is useful over a wide range of applications and which has increased flexibility to respond to changing conditions.